Am I alone in finding it a bit suspicious that Nikon magically found a way to jump from their previous highest native ISO of 12800 to this stunning 104k ISO in an "overnight" response to Canon's 1DX and its native 51200 ISO? If Nikon announced a D4 with the same ISO as the 1D X for release some 6-8 months from now, I would have a much easier time believing it...but this really smells of fresh fish.
I would also expect competition on all fronts, not just the ISO front. FPS, AF capabilities and performance, etc. It seems a bit odd that Nikon would release competition to the 1DX before they even have a chance to get their hands on one and make sure their next flagship really is competition...
I think you're missing the point a little with this release.
The only real complaint the Nikon lot have with their D3s is the small MP size. Most of the pros only wanted 16, 18 at a push. We have to remember, at this level we are talking about a tool for a job, not something with which to practice a hobby and enjoy creating art.
The torch was not Nikon's to gain, but Canons to try and get back. Realistically, how many people will jump ship from this to the 1DX? Not very many - it will be enough to keep the Nikon pros happy.
As for how relevant is high ISO in the real world? Whose real world are you talking about?
Or the press photographer who gets a grainy picture of a paramedic pumping attending Princess Diana in a poorly lit tunnel at 2 or 3 in the morning? Even as a Train Driver, high ISO was an important aspect of 'my real world'.
These cameras are designed to 'get that pic' that pays the rent under almost any condition, and i'm fairly sure that they will both do that - just that on current specs, Canon have regained the flagship pro series mantel from Nikon.